Fuel cells have been proposed as a clean, efficient and environmentally responsible power source for electric vehicles and various other applications. A plurality of fuel cells can be stacked together in series to form a fuel cell stack capable of supplying a desired amount of electricity. The fuel cell stack has been identified as a potential alternative to the traditional internal-combustion engine used in automobiles.
One type of fuel cell is known as a proton exchange membrane (PEM) fuel cell. The PEM fuel cell typically includes three basic components: a cathode, an anode, and an electrolyte membrane. The electrolyte membrane is generally sandwiched between the cathode and the anode. The fuel cell generally also includes porous conductive materials, known as gas diffusion media, which distribute reactant gases over the surfaces of the cathode and anode. The reactant gases typically include hydrogen gas and oxygen can be supplied from air, for example. The hydrogen is delivered to the anode and is converted to protons. The protons travel through the electrolyte to the cathode. The electrons in the anode flow through an external circuit to the cathode, where they recombine with the oxygen and the protons to form water. The electron flow through the external circuit allows the fuel cell to be employed as a power source.
The cathode, anode, and electrolyte membrane are generally interposed between a pair of electrically conductive fuel cell plates to complete the PEM fuel cell. The plates serve as current collectors for the anode and cathode, and have appropriate flow channels and openings formed therein for distributing the fuel cell's reactant gases over the surfaces of the respective cathode and anode. The flow channels generally define lands therebetween that are in electrical contact with the gas diffusion media of the fuel cell. Typically, the plates also include inlet and outlet apertures which, when aligned in a fuel cell stack, form internal supply and exhaust manifolds for directing the fuel cell's reactant gases and liquid coolant to and from, respectively, the anodes and cathodes.
During operation of the fuel cell, water from both the electrochemical fuel cell reaction and external humidification may enter the flow channels. The water is typically forced through the flow channels by the reactant gas, the pressure of which is a primary mechanism for water removal from the flow channels. When the reactant gas flow is not sufficient, however, such as when the fuel cell is operating at a lower power output, water can accumulate or “stagnate”. Stagnant water can block flow channels and reduce the overall efficiency of the fuel cell. Stagnant water may also increase flow resistance in particular flow channels and divert the reactant gases to neighboring channels, resulting in a localized starvation of the fuel cell. The accumulation of water can also lead to a higher rate of carbon corrosion and a poorer durability under freezing conditions. Water accumulation can eventually lead to a failure of the fuel cell.
It is known in the art to employ fuel cell plates having at least one of a hydrophilic coatings and a hydrophobic coating that facilitate the removal of water from the fuel cell. The fuel cell may also include other means of drainage, such as a foam, a wick, a mesh, or other water removing structures adapted to facilitate removal of water from the fuel cell plates.
The fuel cell plates are typically coated, for example, by at least one of spraying, brushing, rolling, printing, and dipping. One known high performance coating is X-TEC® high performance inert nanoparticle coating, commercially available from Nano-X, GmbH in Saarbruecken-Guedingen, Germany. Certain types of coatings, such as various silica-based coatings, are produced by known sol-gel techniques. Vacuum assisted techniques such as physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), and plasma-enhanced chemical vapor deposition (PECVD) methods for coating fuel cell plates are also known. Controlling coating characteristics such as thickness, morphology, and contact angle can be difficult with many of the known coating methods. Certain of the known methods are also prohibitively expensive.
There is a continuing need for a method of coating fuel cell components with at least one of a hydrophilic coating and a hydrophobic coating to facilitate a removal of water from the fuel cell. Desirably, the method is less complex, less expensive, and provides a coating of sufficient durability to be used in the fuel cell.